Secondary lubrication system with injectable additive

ABSTRACT

A lubrication system includes an additive and a delivery system. During normal operational conditions, the lubricating oil circulating in the transmission system is collected and contained in a secondary oil reservoir to retain a quantity of the lubricating oil for use in an oil-out condition. When an oil-out condition is detected, the additive is injected and mixed with the collected lubricating oil in the secondary oil reservoir or dispersed directly into a power transmission gearbox housing to enhance the characteristics of the lubricating oil and increases the operational time period of the power transmission gearbox during an oil-out condition.

RELATED APPLICATIONS

This application is a continuation of prior U.S. application Ser. No.11/610,548, filed Dec. 14, 2006, the entirety of which is hereinincorporated by reference.

U.S. application Ser. No. 11/610,548 claims the benefit of U.S.Provisional Patent Application Ser. No. 60/756,917, filed Jan. 5, 2006,the entirety of which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a lubrication system, and moreparticularly to a secondary lubrication system that incorporates aconcentrated lubricating oil additive selectively injected into thesecondary lubrication system to enable prolonged oil-out operation.

Rotary-wing aircraft power transmission systems incorporate a multitudeof gears and bearings which are subject to heat, sliding and surfacewear. Such conditions are significantly increased during oil-outoperating conditions caused by, for example, ballistic damage, pumpfailure and system leaks. The primary components of a power transmissionsystem which may be failure points under oil-out conditions includebearings and gears which are constantly oil lubricated under normalconditions using pressurized oil jets or splash oil lubrication methods.

The United States Department of Defense (U.S. DoD) currently imposes arequirement that all rotary-wing aircraft power transmission systemsoperate for a predetermined period of time in an oil-out condition. Therequirement includes the capability to maintain flight operations for 30to 60 minutes during the oil-out condition, albeit at reduced powerlevels, sufficient only to sustain level flight operations.

Various emergency or secondary lubrication systems are known andpracticed. Lubricating wicks and jets have been provided for lubricatingindividual components along with a small recirculation system. Airaspirated nozzles have also been utilized for delivering a stream of oilto each individual component. Even through relatively effective, theseexisting systems have not completely satisfies the U.S. DoD imposedrequirements.

Accordingly, it is desirable to provide a secondary or emergencylubrication system which allows a power transmission system to operatefor a prolonged time period under oil-out conditions.

SUMMARY OF THE INVENTION

The lubrication system according to the present invention includes alubricating oil additive and a delivery system. During normaloperational conditions, the lubrication oil which circulates in thetransmission system is collected in a secondary or “emergency” oilreservoir for use in an oil-out condition. When an oil-out condition isdetected, an additive is injected and mixed with the collectedlubricating oil in the secondary oil reservoir or dispersed directlyinto a transmission gearbox housing. Upon mixing with the lubricatingoil, the additive enhances the characteristics of the lubricating oil toenhance prolonged oil-out operation. Alternatively, on the detection ofan oil-out situation, an auxiliary oil supply comprising a lubricantthat contains additives for enhanced survival would be activated toinject the enhanced lubricant directly into a transmission gearboxhousing.

The lubrication system provides a typical power transmission system morethan double the time period under which the transmission system mayotherwise operate under an oil-out condition. Moreover, the lubricationsystem is capable of satisfying the U.S. DoD imposed requirements forall areas/components within the power transmission system.

The present invention therefore provides a secondary or emergencylubrication system which allows the power transmission system to operatefor a prolonged time period under oil-out conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

FIG. 1 is a general perspective view an exemplary rotary wing aircraftembodiment for use with the present invention;

FIGS. 2A and 2B are block diagrams of a lubrication system according tothe present invention;

FIG. 3 is a schematic diagram of a drip type of lubricating oil deliverysystem; and

FIG. 4 is a schematic diagram of a mist type of lubricating oil deliverysystem.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 schematically illustrates a rotary-wing aircraft 10 having a mainrotor system 12. The aircraft 10 includes an airframe 14 having anextending tail 16 which mounts a tail rotor system 18, such as ananti-torque system. The main rotor assembly 12 is driven through a mainpower transmission gearbox (illustrated schematically at 20) by one ormore engines E. Although a particular helicopter configuration isillustrated and described in the disclosed embodiment, otherconfigurations and/or machines, such as ground vehicles, jet aircraft,turbofan engines, high speed compound rotary wing aircraft withsupplemental translational thrust systems, dual contra-rotating, coaxialrotor system aircraft, turbo-props, tilt-rotors and tilt-wing aircraft,will also benefit from the present invention.

The main power transmission gearbox 20 carries torque from the engines Ethrough a multitude of gear train paths to a main rotor shaft 22 of themain rotor system 12. The gearbox 20 is preferably located within ahousing 24 which may at least partially support the main rotor shaft 22.The invention described herein is best illustrated by reference to theillustrated rotary-wing aircraft main power transmission gearbox havinghighly-loaded torque transmitting gears and bearings, however, it willbe appreciated that the inventive teachings are applicable to any systemwhich may require oil-out operation.

Referring to FIG. 2A, a lubrication system 26 communicates with thegearbox 20 within the housing 24. The lubrication system 26 generallyincludes a primary oil reservoir 28 and an “emergency” or secondary oilreservoir 30 which retains a quantity of lubricating oil for use under“emergency” conditions such as an oil-out condition. Various primarycommunication systems 32 such as pumps and the like are utilized tocirculate lubricating oil from the primary oil reservoir 28 into thehousing 24 and to other high friction locations to provide for effectiveoperation of the gearbox 20 and other system during normal operationalconditions. The primary communication systems 32 need not be describedin detail herein as various systems may be utilized in accordance withthe principles of the present invention. Furthermore, it should beunderstood that various lubricating oils may also be used herewith, suchas, for example, DOD-L-85734 or MIL-PRF-23699.

Preferably, a quantity of lubricating oil contained within the secondaryoil reservoir 30 is interchanged with operating lubricating oil duringnormal operational conditions of the lubricating system 26. That is, thelubricating oil may be circulated through the secondary oil reservoir 30such that the lubricating oil contained therein is refreshed yet alwaysmaintained in an essentially filled condition during normal operationalconditions. Although the secondary oil reservoir 30 is illustratedwithin the housing 24, it should be understood that other locationsoutside or partially inside and outside of the housing 24 may also beutilized with the present invention.

Various secondary communication systems 34 such as a drip tank system 36(FIG. 3), an oil mist system 38 (FIG. 4) as well as other “emergency”delivery systems are utilized to communicate the quantity of lubricatingoil contained within the secondary oil reservoir 30 into the housing 24and to other high friction locations to provide for short term operationof the gearbox 20 and other system during oil-out conditions. It shouldbe understood that the secondary communication system 34 may be ofvarious forms and may be integrated or separate from primarycommunication system 32.

An additive reservoir 40 contains an additive which is selectivelyinjectable into the secondary oil reservoir 30 by a delivery system 42to enhance the characteristics of the lubricating oil collected in thesecondary oil reservoir 30 in response to an oil-out condition. Thedelivery system 42 communicates the additive from the additive reservoir40 into the secondary oil reservoir 30. Preferably, the delivery system42 includes a pressurization system which injects and mixes the additiveinto the lubricating oil collected in the secondary oil reservoir 30prior to communication into the housing 24. Alternatively, the oiladditive substance is not stored separately, but contained within thesecondary oil reservoir 30 but only mixed with the collected lubricatingoil during oil-out operation.

Alternatively or in addition thereto, a delivery system 42A (FIG. 2B)communicates the additive from the additive reservoir 40 directly intothe housing 24. The delivery system 42A releases the additive into theatmosphere of the housing 24 separately from the lubricating oildelivered from the secondary oil reservoir 30. The injection of theadditive into the housing 24 essentially coats the entire interiorcontents of the gearbox 20 to enhance the functional surfaces of thebearings and gears therein. The delivery system 42A may be pressurizedby relatively small lightweight pressure canisters or may be attached toa remote air pressure device such as a bleed air source.

The delivery system 42, 42A additionally includes either or both of anautomatic or manual control system 44 to control injection of theadditive. That is, the lubrication system 26, 26A may include either orboth of an automatic check system such as an electro-mechanical systemutilizing pressure monitoring sensors and/or require the involvement ofa pilot operation manual initiator in the decision loop to initiateoperation of the delivery system 42, 42A to minimize a false detectionof an emergency oil-out condition. This is preferred because theadditive may have long term corrosive or other detrimental effects onthe gearbox 20 due to the chemical aggressiveness of the additives.

A wide variety of additives may be utilized. Preferably, however, theadditive is selected based upon elemental testing and demonstratedperformance in the areas of reduced friction, reduced heat generation,film forming capability, and chemical interaction with the gears andbearings. More preferably, the additive includes high concentrations ofanti-wear (AW) and extreme-pressure (EP) compositions. Typically,phosphates are used as AW and EP additives. Specific additives may beselected according to their activation temperature and othercharacteristics. The additive also may preferably form, through areaction of the nascent or oxidized moving component surface, aprotective film on the surface thereof.

Alternatively, the additive need not necessarily be lubricious but onlyhave desirable characteristics such as: an appropriate melting orvaporization temperature; high specific heat (heat capacity); and/orhigh latent heat of fusion or vaporization. During an oil-out condition,temperature control may be more important than lubrication, althoughboth of these factors are important and somewhat interdependent. Toachieve improved wetting (coverage) of the moving component surface andthereby increase moving component cooling, especially in the possiblepresence of residual lubricating oil, a non-polar liquid assists withmiscibility of the lubricant. Alternatively, while being a polar liquid,water is also a candidate whose thermal properties meet the requirementsand whose polarity can be modified by the addition of certain soaps orother substances that possess both polar and non-polar characteristics.

Although particular step sequences are shown, described, and claimed, itshould be understood that steps may be performed in any order, separatedor combined unless otherwise indicated and will still benefit from thepresent invention.

The foregoing description is exemplary rather than defined by thelimitations within. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, one ofordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. For thatreason the following claims should be studied to determine the truescope and content of this invention.

What is claimed is:
 1. A lubrication system to lubricate movingcomponents comprising: an oil reservoir for storage of a quantity ofcollected lubricating oil; an additive stored under normal operationalconditions; and a controller which causes an injection of said additivein response to an oil-out condition.
 2. The system as recited in claim1, wherein said quantity of collected lubricating oil within said oilreservoir is received and interchanged from a primary lubricating oilreservoir during the normal operational condition.
 3. The system asrecited in claim 1, wherein substantially all of said additive isselectively injectable into said oil reservoir in response to theoil-out condition.
 4. The system as recited in claim 1, whereinsubstantially all of said additive is selectively injectable at one timeinto a rotary-wing aircraft transmission gearbox housing which at leastpartially encloses the moving components.
 5. The system as recited inclaim 1, wherein said additive includes an anti-wear (AW) composition.6. The system as recited in claim 1, wherein said additive includes anextreme-pressure (EP) composition.
 7. The system as recited in claim 1,wherein said additive includes an anti-wear (AW) and an extreme-pressure(EP) composition.
 8. The system as recited in claim 1, wherein saidadditive forms a protective film on the moving components.
 9. The systemas recited in claim 1, wherein said additive includes a non-polarsubstance miscible with the collected lubricating oil.
 10. The system asrecited in claim 1, wherein said additive includes a polar substancenon-miscible with the collected lubricating oil.
 11. The system asrecited in claim 1, wherein said additive includes a phosphate.
 12. Thesystem as recited in claim 1, wherein said additive is injected underpressure by a delivery system during the oil-out operational condition.13. The system as recited in claim 1, wherein said additive includes asubstance with a boiling point to increase cooling capability as saidsubstance changes phase.
 14. The system as recited in claim 1, whereinsaid additive includes at least one substance with a specific heatgreater than that of said lubricating oil.
 15. The system as recited inclaim 1, wherein said controller includes a manual control system. 16.The system as recited in claim 1, wherein said controller includes anautomatic control system.
 17. A lubrication system to lubricate movingcomponents comprising: a primary oil reservoir; a secondary oilreservoir in communication with said primary oil reservoir, a quantityof collected lubricating oil from said primary oil reservoir circulatedthrough said secondary oil reservoir such that said quantity ofcollected lubricating oil contained therein is refreshed and maintainedin an essentially filled condition under normal operational conditions;an additive stored under normal operational conditions; and a controllerwhich causes injection of said additive into said secondary oilreservoir in response to an oil-out condition.
 18. The system as recitedin claim 17, wherein said quantity of collected lubricating oil withinsaid oil reservoir is received and interchanged from a primarylubricating oil reservoir during the normal operational condition. 19.The system as recited in claim 17, wherein substantially all of saidadditive is selectively injectable into said oil reservoir in responseto the oil-out condition.
 20. The system as recited in claim 17, whereinsubstantially all of said additive is selectively injectable at one timeinto a rotary-wing aircraft transmission gearbox housing which at leastpartially encloses the moving components.